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Question

Expand the following, using suitable identities:
1)(3a7bc)2.
2)(x+2y+4z)2 [4 MARKS]


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Solution

Formula: 1 Mark
Application: 1 Mark each
Answer: 0.5 Mark each

(a+b+c)2=a2+b2+c2+2ab+2bc+2ca ..identity(i)

1)(3a7bc)2

a=3a,b=7b,c=c [comparing with identity(i)]

=(3a)2+(7b)2+(c)2+2(3a)(7b)+2(7b)(c)+2(c)(3a)

=9a2+49b2+c242ab+14bc6ac


2)(x+2y+4z)2

a=x,b=2y,x=4z [comparing with identity(i)]

=x2+(2y)2+(4z)2+2x(2y)+2(2y)(4z)+2(4z)x

=x2+4y2+16z2+4xy+16yz+8zx


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